Super engineering plastics, such as aromatic polyetherketone resins (polyaryletherketone resins), are known as a thermoplastic resin having excellent heat resistance and mechanical strength, while some super engineering plastics have poor light resistance. For that reason, various resin characteristics are often changed under a light environment.
As a method for improving the light resistance, for example, addition of a widely used stabilizer (such as a light stabilizer or an antioxidant) has been examined. Unfortunately, the widely used stabilizer is thermally decomposed in the process of molding (fabrication) due to a very high melting point or a molding temperature (fabrication temperature) of the super engineering plastic, and the addition sometimes fails to sufficiently improve the light resistance. Further, in addition to the simple thermal decomposition, the resulting decomposition product of the stabilizer sometimes causes the resin to be more viscous and to have a lower heat resistance.
Japanese Patent Application Laid-Open Publication No. 2006-274073 (JP-2006-274073A, Patent Document 1) discloses a resin composition comprising (A) 70 to 99% by mass of a polyarylketone resin and (B) 30 to 1% by mass of a fluorinated resin, wherein the fluorinated resin (B) dispersed in the resin composition has an average particle diameter of 0.1 to 30 μm. This document also discloses that the resin composition provides a resin molded product having excellent sliding properties, solvent resistance, and heat resistance.
WO2012/005133 (Patent Document 2) discloses a resin composition for the purpose of improving sliding properties and impact resistance; the resin composition comprises an aromatic polyetherketone resin and a fluorinated resin, the fluorinated resin being a copolymer of tetrafluoroethylene and a perfluoroethylene unsaturated compound, the composition comprising the aromatic polyetherketone resin and the fluorinated resin at a mass ratio of 95:5 to 50:50, the fluorinated resin being dispersed as particles in the aromatic polyetherketone resin and having an average dispersed particle size of not more 3 μm.
New light sources, such as a light emitting diode (LED: Light Emitting Diode), having advantages of less electricity consumption and much longer life, are increasing in demand as lighting, display devices, and others. An LED generally comprises a light-emitting semiconductor portion, a lead wire, a reflector serving as a housing, and a transparent sealant for sealing the semiconductor. Among these components, as the reflector part, products made of various materials (such as a ceramic or a heat-resistant plastic) are commercially available. The problem with a ceramic reflector is a low production efficiency. Whereas, the problem with a heat-resistant plastic reflector is decrease in light reflectance due to discoloration in an injection molding step (330° C., for several minutes), a step of heat-curing a conductive adhesive or a sealant (100 to 200° C., for several hours), a soldering step (particularly, a peak temperature of not lower than 260° C. for several minutes in use of a lead-free solder (e.g., a tin-silver-copper alloy-based solder) in surface-mount technology (SMT)), or under an actual environment. In particular, a widely used heat-resistant polyamide easily changes color by heating, and the decrease in light reflectance cannot be disregarded.
As polyamide resin compositions for LED reflector, some resin compositions comprising polyamide resins and various additives have been reported [for example, Japanese Patent Application Laid-Open Publication No. 2-288274 (JP-2-288274A, Patent Document 3), Japanese Patent No. 4892140 (JP-4892140B, Patent Document 4), Japanese Patent No. 4525917 (JP-4525917B, Patent Document 5), and Japanese Patent Application Laid-Open Publication No. 2011-21128 (JP-2011-21128A, Patent Document 6)].
The current LED application is mainly an extremely low-powered product (such as liquid crystal television or room lighting). In the future, a greater demand for a high-powered LED will probably be anticipated for applications that need more brightness, including 3D television, lighting for automobile use (such as a headlight), and outdoor lighting.
The high-powered LED requires such a high luminance, and the LED (including a package thereof) also requires an excellent durability against generation of high heat with high power (or output). However, the existing composition for a reflector has a difficulty in a long-term durability under a high temperature (in particular, not lower than 150° C.), and it is considered that the existing composition is unsuited for the high-powered LED.
Meanwhile, a ceramic substrate that is being generally used for a high-powered LED application is heat-resistant. Unfortunately, the ceramic substrate has a problem of a lower production efficiency compared with a resin substrate, because the resin substrate is obtainable by injection molding.
Incidentally, an aromatic polyetherketone resin usually having a heat resistance higher than that of a polyamide resin is not being used for a LED reflector, probably because it is easy to predict decrease in physical properties or change in color (e.g., yellowing) of the aromatic polyetherketone resin due to a poor light resistance thereof as described above.